A standard flow control valve such as described in German patent 3,127,738 of M. Pawelzik or in commonly owned U.S. patent application Ser. No. 08/046,005 filed 9 Apr. 1993 by F. Wagner et al has a housing having a chamber into which opens a port, a ceramic valve plate fixed in the chamber over the port, formed with a throughgoing aperture aligned with the port, and having a substantially planar face, and a ceramic control plate having a substantially planar face lying flatly on the valve-plate face and formed with a throughgoing aperture. The control plate can be pivoted relative to the valve plate about an axis substantially perpendicular to and traversing the surfaces between an open position with the control-plate aperture overlapping the valve-plate aperture and a closed position with the control-plate aperture aligned axially with a portion of the valve-plate face and offset angularly from the valve-plate aperture and with the valve-plate aperture aligned axially with a portion of the control-plate face and offset angularly from the control-plate aperture.
The maximum angular stroke or travel of such a valve is normally 180.degree. between the fully open and the fully closed positions. Due to this relatively short stroke, it is common for the user to simply flip the valve to the fully open position, even though that is rarely needed. Clearly this can waste the fluid being dispensed, normally water.